system.net.mail requires starttls

how to I fix I get an error that it requires a starttls
Imports System.Net.Mail
Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try

            Dim SmtpServer As New SmtpClient()
            Dim mail As New MailMessage()
            SmtpServer.Credentials = New Net.NetworkCredential("me@gmail.com", "password")
            SmtpServer.Port = 587
            SmtpServer.Host = "smtp.gmail.com"
            mail = New MailMessage()
            mail.From = New MailAddress("me@gmail.com", "my name")
            mail.To.Add("me@hotmail.com")
            mail.Subject = "Test Mail"
            mail.Body = "This Is for testing SMTP mail from GMAIL"
            SmtpServer.Send(mail)
            MsgBox("mail send")
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
End Class